Final answer:
Formal charge (Fc) can be calculated using the formula Ve - (B + Nb), where Ve is valence electrons, B is the number of bonds, and Nb is nonbonding electrons. In CH2O, the Fc of carbon is 0, while in HCN, the Fc of carbon is -1.
Step-by-step explanation:
Formal charge (Fc) is calculated using the formula Fc = Valence electrons - (Bonds + Nonbonding electrons). For example, in the molecule CH2O, carbon has 4 valence electrons, forms 4 bonds, and has no nonbonding electrons, so the formal charge of carbon is 0. On the other hand, in the molecule HCN, carbon has 4 valence electrons, forms 3 bonds, and has 1 nonbonding electron, so the formal charge of carbon is -1.